Stabilization of oil well fluid



Jan. 31, 1961 F. E. GILMORE STABILIZATION OF OIL WELL FLUID Filed May 20, 1955 INVENTOR. E E.G|LMORE ATTORNEYS Still another object of my invention is to provide a prac-, tical and economical method for stabilizing crude oil against evaporation losses in atmospheric storage and de livering the recovered gas at suflicient pressure for trans STABILIZATION OF OIL WELL FLUID Forrest E. Gilmore, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Filed May 20, 1955, Ser. No. 509,850

6 Claims. (Cl.208-361) .This invention relates to a method of separating oil wellfluid into oil and gas. In one aspect, it relates to a method for removing practically all of the butanes and lower boiling hydrocarbons as gas from well fluid from a flowing well so as to at least minimize atmospheric storage losses. 'In another aspect, it relates to a method for stabilizing well fluid in the field without the use of steam or fired heaters by employing hot compressed gases, engine cooling water, and previously heated stabilized oil to supply all of the heat requirements for the stabilization operation.

In oil field production operations, in many cases, when newly produced oil is stored in lease storage tanks open to the atmosphere, considerable amounts of the most volatile hydrocarbon constituents of the oil vaporize into the atmosphere. This vaporization results in loss of hydrocarbons, and obviously, such loss cannot ever be recovered. In the field, there are usually not available fired heaters orsteam boilers for supplying heat for stabilization of crude oil against atmospheric storage losses.

I have devised a method for at least partially stabilizing crude oil against atmospheric evaporation which does not necessitate the use of fired heaters or steam generating boilers. According to my process, I have found that the heat available from compressed gases, from the cooling water of the compressor engine and from the stabilized oil, is sutficient to stabilize the oil to such an extent that practically all of the butanes and lighter can be removed from the oil and recovered as gas.

- According to.my invention, oil from a well or other source at a reasonably high pressure is flash-vaporized to remove at least a portion of the more easily vaporizable constituents. The residue liquid from the flashvaporization operation is heated to a temperature substantially higher than the temperature of the aforesaid flash-vaporization, and at this higher temperature, the oil is again flashed and at a still lower pressure. To heat the residue liquid from the first flashing step to the higher temperature I heat exchange this first flashed oil with a higher temperature flash residue, with hot compressed gases from a compressor and with hot compressor engine cooling water, the compressor compressing the flashed gases from the two flashing steps to such a pressure as desired for delivery to a pipe line. I find that heat from these three. sources is ample for heating the crude oil for its final flashing to produce a substantially stabilized crude oil.

The invention will be further described with such reference to the stabilization of crude oils, it being understood that other oils or liquids can be treated according to the method or procedure of the present invention.

1 An object of my invention is to provide a practical and economical method for stabilizing crude oil in the field against atmospheric vaporization losses.

Another object of my invention is to provide a method for removing practically all of the butanes and lower boiling hydrocarbons asrecovered gas from the fluid from a flowing well.

mission to a pipe line.

Yet another object of my invention is to provide an assembly of apparatus by which heat for at least partial stabilization of crude oil can be obtained without the use of steam or fired heaters, and the cooling oi. compressed gases, engine cooling water and stabilized oil is ob tained without the usual cooling water supply or cooling towers.

Still, other objects and advantages of my invention will be realized upon reading the following disclosure, which taken with the attached drawing, forms a part of this specification.

. The drawing represents in diagrammatic form, arrangement of apparatus parts, for carrying out the process of my invention.

Referring to the drawing, well fluid from well 1 or other source flows through a pipe 2 into a flash separator tank 3. Oil remaining from the flashing operation in tank 3 is removed therefrom through a pipe 8 and is passed through heat exchangers 10, 11 and 12, and thence through a pipe 13 into a second flash separator tank 14. The flow of flash bottoms from separator tank 3 is regulated by a float-controlled valve 9, the float operating in response to the liquid level in the separator. In

passing through this valve 9, pressure on the oil is re-.

duced to such an extent that further flashing takes place in the flash separator 14. Flashed vapors from separator 14 are passed through a pipe 15 into the low pressure stage 16 of a compressor. Compressed gas is passed through a pipe 5 into a high pressure compressor stage 6 from which the hot compressed gas passes on through a pipe 17 to one side of the heat exchanger 11. After passing through heat exchanger 11, the gases are passed through a pipe 18 for delivery to a pipe line or such other disposal as desired.

The flashed gases from the first flash vaporization are Withdrawn from flash chamber 3 and are delivered through pipe 4 into the second compression stage 6 via pipe 5. Thus, the first flash gases are combined with the gases from the second flashing step for final compression and passage through heat exchanger 11.

An internal combustion engine 7 is provided for operating the compressor, and this internal combustion engine is cooled with such a coolant as water. Hot water from the cooling system of the compressor is passed through a pipe 21 into the heat exchanger 12 while a pipe 22 returns the cooling water from exchanger 12 to the low temperature side of the compressor cooling system. Pipe 19 is provided for removal of the flashed oil from the flash separator 14, and this pipe delivers this hot flashed oil to the heat exchanger 10.- After passing through heat exchanger 10, the oil is removed therefrom through a pipe 20 and is delivered to oil storage, or such other disposal as desired.

J As a means for cont rolling the operation in heat exchanger 11, I provided a bypass pipe 25 connecting pipes 17 and 18. In this bypass pipe 25 is disposed a motor valve 24- which operates in response to a temperature control apparatus 23. This temperature controller operates in response to a thermostatic element 26 disposed in pipe 13. This thermostatic element 26 can be disposed in pipe 13, as illustrated, orit can be disposed equally well in pipe 15 or in pipe 19, since the temperatures of the materials flowing through each of these three pipes are inter-related.

. Asan example of the operation of this apparatus for stabilizing a well fluid, I will describe its operation em- Patented Jan. 31, 1961 One ploying :acrude oil produced in Andrews County, Texas. Such a-well fluid ispassed into separator 3 at such a temperature that when the pressure in this separator is maintained at about 50 p.s.i.g.', the temperature Within 4 flash oi evaporate in atmospheric storage with large attendant losses. As an example of the results of the stabilization of a crude oil when using my method in comparison to conventional oil-field practice of affecting the separathe separator is about 60 F. Flash bottoms are removed 5 tion at 20 p.s.i.g. and 60 F. are the following data. thr'oughpipe 8', through the float controlled valve 9, and These data are based on 2,000 ar p day ofthe passed onthrough the three heat exchangers and through above-mentioned Andrews County crude oil production: pipe 13 into the separator 14. Heat exchangers 10, 11 Wlth the conventional oil-field practlce the gas and and 12 are so operated that the contents of the separator Oil contain hght hydrocarbons as follows: 14'have a temperature of about 120 F. under a pres- 1O sure of about 2 p.s.i.g. Flash bottoms from separator 111 Gas In on 14 at about 120 F. are then heat exchanged with the oil flowing through pipe 8, the flash bottoms entering ex- GaL/Day Percent GaL/Day Percent changer having the above-mentioned temperature of about 120 F. and an outlet temperature of about 75 F. 15 lentane and Hexane 933 9.0 9, 639 91.0 The'compre'ssor stages 16 and 6, operating to compress gfgggZ- 21138 3%? i 3;; the flashed gases from pipe 15 and pipe 4, deliver the r complessed gases at abqut 200 at about 230 With my method the following comparative separation the high temperature side of exchanger 11 and glve p is found. sufiicient of their heat so that the effluent gases have a 20 temperature of about 108 F. Thus, the gas flows from exchanger 11 at about 108 F. under about 200 p.s.i.g., In on 335 33 3; ggg g g ggg ggl 3 .35., 5...... 3.1.5,, 53...,

The final stage of heat exchange occurs in exchanger 5 p r 12 upon flow of hot coolant from the compressor engine Pentane and Hexane 31 122 E81 2; through pipe 21 at about 150 F. into this exchanger. Propane 5-140 826 The coolant leaves exchangerlZ at about 140 F. for its return trip to the compressor" engine. From these data, it will be observed that when stabiliz- For cooling the engine water from about 150 F. to ing such a crude oil accordingto my invention, only 826 about 140 F., I find that cooling water must be circulated gallons of propane remain in the oil While 1,966 gallons at h f about 7 of propane remain in the oil when the oil is flashed at Upon passing through these three stages of heat ex- 20 p.s.i.g. in the above-mentioned conventional field operchange, the flash bottoms from flash separator 3 are P In open 3 Storage substaqhal por,tlon of heated from about 60 F. to such a temperature that after thls 1,966 gallons of Propane t h wlth conslflerzfble flashing in separator 14, the bottoms therein have the amounts of more Valuable h would vaporlzs P of 23133333323?1133.333:1333 3 3332; .These fibovemennoned temperatures and pressures. enthe stabilization method of my invention might be lost 9 9 Water q rate are all based on the 49 by evaporation, this loss'is usually negligible. Similar stabihzation of a sufficlent quantity of an Andrews County, results are obtained when considering butanes Since by j? 011 to glve 2,000 barrels Per Stream day of my method of stabilization, 2,222 gallons are left in the Stablhzed' oil in contrast to 3,430 gallons left in the oil by conven- Table I gives the compos1t1ons of the crude 011 well tional separation at 20 i and Of the several products in transit from One piece The diflerence in the volume f the propane and of the pp r another, and of the final gas and liquid butanes in the oil stabilized according to' my invention, products of my stabilization process. and that from' the oil separated at 20 p.s.i.g. are included Table I 2Well 3111111 4133511411 Gas 15-Flashed Gas S-Fl. Bottoms 203mb. Or. 011 18-G'as' Product Mols/SD Gals/SD Mols/SD Gals/SD Mols/SD Gals/SD Mols/SD Gals/SD Mols/SD Gals/SD Mols/SD Gals/SD 1,533 9,324 1, 453 s, 742 73.0 566 75 532 2.0 16 1,531 9, 308 421 4, 074 321 3, 10s as. 9 860 100 966 11. 1 106 409. 9 3, 938 574 5,966 275 2, 853 219.1 2, 234 299 3,110 79.9 826 494.1 5,140 464 5, 563 102 1,224 177.2 2,122 1 362 4,344 184.8 2,222 279.2 3,346 332 5, 250 25.8 354 84.9 1,170 356.2 4,896 271.3 3,726 110.7 1,524 329 5, 122 6. 3 99 30. 7 430 322. 7 5, 023 292. 0 4, 543 37. 0 579' 2, 331 72, 613 1.3 p 0.5 15 2,379.7 72, 57s 2,379.2 72, 563 1.3

In the above table, it is noted that the gas product (at in the gaseous" product from my two flash vessels, and a pressure of 200 p.s.i.g.) is equivalent to 23,920 gallons these quantities of propane and butane in the gas are then perstream day. This gas product is suitable feed stock recovered in a gasoline extraction plant as natural gasofor a natural gasoline extraction plant, and when so procline, propane and butane products. I essed, should yield about 3,060 gallons per day of 26-lb. It will be understood that the specific conditions of Reid vapor-pressure gasoline, about 2,444 gallons per day temperature and pressure hereinbefore stated are not critiof butane, and assuming 100% recovery, about 5,140 galcal to the invention, nor to'the method of operating as lons per day of propane as liquid products. herein set forth, in the sense that given the particular Usually, the complete stabilization of well fluid is not economically justified in the field, but a method such as theone which I have herein disclosed is needed to stabilize at least partially a crude oil to remove the butane and lower boiling hydrocarbons'without removing'too method of operating, one skilled in the art can, for each liquid to be stabilized, select optimum conditions. Thus, the invention isessentially a' combinationof steps as'set forth herein, and in thedrawing; in theuse'of heat of compression of the gases, and theheat of the engines cool much of th'e 'pentanes -ahd heavier, so that the oil will'not' ing water, and the heat of the finally stabilized product as used byway of heat exchange to-supply all of the heat required for the stabilization.

' Reasonable variations and modifications are possible within the scope ofthe foregoing disclosure, drawing, and the appended claims to the invention, the essence of which is that the heat requiredfor stabilization of a crude oil is supplied by the heat of compression of the stabilizer gases and the compressors cooling water along with heat supplied from the final stabilization product, makes a self-sufiicient process as regardsheat required for the stabilization.

In addition to the finally stabilized oil supplying a portion of the heat for heating the crude oil for the final stabilization step, this heat exchange provides a cooling step for the finally stabilized oil so that its-temperature is reasonably low as it leaves my system for passage to storage. Thus, by making certain that the crude oil passing to storage is at a reasonably low temperature and low vapor pressure vaporization losses are minimized.

As mentioned hereinbefore, important advantages of my operation are that cooling towers and large supplies of cooling water are not required. Also, fired heaters or steam boilers are not required for supplying heat for effecting the second stage of flashing or stabilization. Thus, the operation of my process is one economically feasible both as regards equipment, maintenance costs, and operating costs for stabilizing crude oils against excessive evaporation losses.

While the pressure stated as being maintained in separator vessel 3 was 50 p.s.i.g., this pressure can vary between the limits of, for example, about 30 to 100 p.s.i.g. Similarly, the pressure stated as being held in separator 14 was given as 2 p.s.i.g. This pressure can be maintained from the limits of about to 5 p.s.i.g. The pressure limits which can be tolerated in flash vessel 14 are much narrower than those in vessel 3 because the flashing operation in vessel 14 must be very carefully controlled in order to give final products of desired compositions. The temperatures which will result in vessel 3 when operated within the above-mentioned pressure range will vary from about 50 to 70 F., and the temperature in separator 14 likewise will vary from about 115 to 125 F. The pres- Sure of the compressed gases issuing from the high-pressure stage 6 likewise can vary between about 150 and 250 p.s.i.g. with attendant changes in temperature. As temperatures and pressures in the separators are varied to fit the particular crude oil being stabilized, it is obvious that temperatures within the several heat exchangers can also vary somewhat from those given hereinabove.

While certain embodiments of the invention have been described for illustrative purposes, the invention is not limited thereto.

I claim:

1. A method for stabilizing crude oil well fluid as it comes from a well at a pressure greater than about 30 to 100 p.s.i.g. comprising reducing the pressure on said crude oil to a pressure within about 30 to 100 p.s.i.g. in a first flashing operation, separating first flashed vapors from a first residue liquid, heating the first residue liquid and further reducing the pressure thereon to about 0 to 5 p.s.i.g. in a second flashing operation, separating second flashed vapors from a second residue liquid, compressing the first and second flashed vapors in an internal combustion engine powered compressor whereby in this compression operation the flashed vapors are heated and the engine coolant is also heated, said heating the first residue liquid being by indirect heat exchange with the compressed and heated flashed vapors and with the heated coolant from said engine, and removing the flashed vapors and the heat exchanged second residue liquid as products.

2. A method for stabilizing crude oil well fluid as it comes from a well at a pressure greater than about 30 to 100 p.s.i.g. comprising reducing the pressure on said crude oil to a pressure within about 30 to 100 p.s.i.g. in a first flashing operation, separating first flashed vapors from a first residue liquid, heating the first residue liquid and further reducing the pressure thereon to about 0 to 5 p.s.i.g. in a second flashing operation, separating second flashed vapors from a second residue liquid, compressing the first and second flashed vapors in an internal combustion engine powered compressor whereby in this compression operation the flashed vapors are heated and the engine coolant is also heated, said heating the first residue liquid being by separate indirect heat exchanges with the second residue liquid, the hot compressed flashed vapors, and the heated engine coolant, and removing the heat exchanged flash vapors and the heat exchanged second residue liquid as products.

3. The method of claim 2 wherein the flashed gases are compressed to a pressure of about 150 to 250 p.s.i.g.

4. A method for separating oil well fluid produced at a superatrnospheric pressuregreater than 30 to -p.s.i.g. into oil and gas comprising separating the Well fluid into a liquid and a gas at a superatmospheric pressure below the first mentioned pressure and within about 30 to 100 p.s.i.g., heating the liquid in an indirect heat exchange operation with hot compressed vapors as subsequently produced whereby the hot compressed vapors are cooled, introducing the heated liquid into a flash zone at a still lower pressure between about 0 and 5 p.s.i.g. and therein separating flashed vapors from a liquid residue, compressing the flashed vapors and separated gas to a pressure between about and 250 p.s.i.g. to produce said hot compressed vapors as subsequently produced, removing said liquid residue as a stabilized oil product of the process, and removing the cooled compressed vapors from the heat exchange operation at a pressure between about 150 and 250 p.s.i.g. as suitable feed stock gas for a gasoline extraction plant.

5. A method for separating oil well fluid produced at a superatmospheric pressure greater than about 30 to 100 p.s.i.g. into oil and gas comprising separating the well fluid into a liquid and a gas at a superatmospheric pressure below the first mentioned pressure and within about 30 to 100 p.s.i.g., heating the separated liquid in a first indirect heat exchange with a hot liquid residue as subsequently produced whereby the hot liquid is cooled, further heating the once heated separated liquid in a second indirect heat exchange with hot compressed vapors as subsequently produced whereby the compressed vapors are cooled, introducing the further heated liquid into a flash zone at a pressure between about 0 and 5 p.s.i.g. and therein separating flashed vapors from a hot liquid residue as said hot liquid residue as subsequently produced, compressing the first separated gas and the separated flash vapors to a pressure between about l50 and 250 p.s.i.g. to produce said hot compressed vaporsas subsequently produced, removing the cooled liquid from its heat exchange as a stabilized oil product of the operation, and removing the cooled compressed vapors from their heat exchange at a pressure between about 150 and 250 p.s.i.g. as suitable feed stock gas for a gasoline extraction plant.

6. A method for separating oil well fluid produced at a superatmospheric pressure greater than about 30 to 100 p.s.i.g. into oil and gas comprising separating the well fluid into a liquid and a gas at a lower superatmospheric pressure than that first mentioned and within about 30 to 100 p.s.i.g., heating the separated liquid in a first indirect heat exchange with a hot liquid residue as subsequently produced whereby the hot liquid is cooled, further heating the once heated separated liquid in a second indirect heat exchange with hot compressed vapors as subsequently produced whereby the compressed vapors are cooled, still further heating the twice heated separated liquid in a third indirect heat exchange with a hot coolant as subsequently produced whereby the hot coolant is cooled, introducing the still further heated separated liquid into a flash zone at a pressure between about 0 and 5 p.s.i.g and therein separating flashed vapors from a hot liquid residue as said hot liquid residue as subsequently produced compressing: the first separated gas and the separated flash vapors in an internal combustion engine powered compressor to a pressure between about 15 0 and 250 p.s.i.g. to produce said hot compressed vapors as subsequently produced and the engine coolant is heated, this heated coolant being the aforementioned hot coolant as subse- ReferencesCited in the-file of this patent UNITED STATES PATENTS 1,619,856 Trent Mar. 8,1927

. 8 1,687,595, Shore Oct. 16 1928 1,758,595 Cattaneo May 13, 19:30 2,2 9,433, Atwell' Apr. 29, 1941 2;25Q,716. Legatski July 29, 1941 2,327,187 Hill Aug. 17, 1943 2,341,389 Rupp et a1 Feb. 8, 1944 2,616,912 Dickinson NOV. 4, 1952 2,630,402 Miller etal. Mar. 3, 1953 2,744,337 Reed et a1. May 8, 1956 2,768,112? Laurence et a1. -1 Oct; 23', 1956 OTHER REFERENCES Perry: Cherriical Engineers Handbook, McG'raw-Hill 15 Book'Col, N.Y., N.Y. ThirdEditiOn (1950), page 1659;

UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No, 2,970,107 January 31, 1961 Forrest-Eb Gilmore It is hereby cert ent requiring cor corrected below.

ified that error appears in the above numbered patrection and that the said Letters Patent should read as Column 5 line 69, before "flashed" insert heat exchanged line 70, strike out "heat exchange".

Signed and sealed this 25th day of July 1961,

C SEA L) Attcst:

ERNEST W. SWIDER Attesting Officer DAVID L. LADD Commissioner of Patents 

1. A METHOD FOR STABILIZING CRUDE OIL WELL FLUID AS IT COMES FROM A WELL AT A PRESSURE GREATER THAN ABOUT 30 TO 100 P.S.I.G. COMPRISING REDUCING THE PRESSURE ON SAID CURDE OIL TO A PRESSURE WITHIN ABOUT 30 TO 100 P.S.I.G. IN A FIRST FLASHING OPERATING, SEPARATING FIRST FLASHED VAPORS FROM A FIRST RESIDUE LIQUID, HEATING THE FIRST RESIDUE LIQUID AND FURTHER REDUCING THE PRESSURE THEREON TO ABOUT 0 TO 5 P.S.I.G. IN A SECOND FLASHING OPERATION, SEPARATING SECOND FLASHED VAPORS FROM A SECOND RESIDUE LIQUID, COMPRESSING THE FIRST AND SECOND FLASHED VAPORS IN AN INTERNAL COMBUSTION ENGINE POWERED COMPRESSOR WHEREBY IN THIS COM- 